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Interactive Control of Carbon Assimilation, Redox Balance, CBB Expression, Nitrogenase Complex Biosynthesis, Hydrogen Production, and Sulfur Metabolism in RubisCO Compromised Mutant Strains of Nonsulfur Purple Bacteria

Laguna, Rick
http://rave.ohiolink.edu/etdc/view?acc_num=osu1285013415

Abstract Details

2010, Doctor of Philosophy, Ohio State University, Microbiology.
The continuation of redox homeostasis is required for bacterial metabolism and cellular integrity. In order to maintain redox balance, multifaceted and integrated regulatory networks are required to respond to variable inter- and intracellular environments. The ability of nonsulfur purple (NSP) photosynthetic bacteria to maintain redox poise during photoheterotrophic growth is remarkable. Crosstalk and coordinated regulation between various systems (DMSO reduction, CO2- and N2-fixation) are employed to maintain redox poise. The use of each system is influenced either by the availability of the preferred terminal electron acceptor or the presence or absence of one system. For example, in Rhodobacter sphaeroides, excess reductant generated during photoheterotrophic growth is consumed by the reduction of metabolically produced CO2 via ribulose 1,5-bisphosphate carboxylase-oxygenase (RubisCO) through the Calvin-Benson-Bassham (CBB) reductive pentose phosphate CO2 fixation pathway. However, when the primary electron sink, the reduction of CO2 is void due to the presence of a non-functional CBB cycle, the use of alternative redox sinks must be employed. For example, derepression of nitrogenase complex synthesis under normal repressive conditions, allows for cellular redox balance through reduction of protons to H2. To further understand cellular processes that are involved in synthesis and consumption of cellular reductant, which can maximize the production of bio-fuels in NSP bacteria, in this dissertation we characterize and probe the role of the CBB cycle in Rhodopseudomonas palustris and Rb. sphaeroides. In addition, we confirm that synthesis of nitrogenase complex and the use of this protein complex to produce hydrogen gas is intimately tied to the regulation of the CBB pathway. Moreover, we show that a mutation in the nifA gene of Rps. palustris RubisCO deletion strain CGA2044 allowed for expression and synthesis of the nitrogenase complex. On the other hand, mutations in both the nifA and glnA genes appeared to allow for expression and synthesis of the nitrogenase complex in Rb. sphaeroides RubisCO deletion strain 16PHC. Further, it was found that Rps. palustris RubisCO deletion strain CGA2044 produced the most hydrogen as compared to other RubisCO deletion strains of NSP photosynthetic bacteria and inactivation of the CBB cycle increased hydrogen production. Rb. sphaeroides RubisCO deletion strain 17 was also isolated and it was shown that expression of the CBB system was down-regulated in this strain as compared to wild-type. The cbbR gene in Rb. sphaeroides RubisCO deletion strains 16, 17, and 16PHC was up-regulated as compared to wild-type. Finally, in Rb. sphaeroides RubisCO deletion strain 16PHG, sulfate reduction, serine-, and cysteine-biosynthesis appeared to play roles in cellular redox balance within this strain, with sulfite reductase, phosphoglycerate dehydrogenase, and cysteine synthase up-regulated as compared to wild-type. In strain 16PHG, the production of hydrogen sulfide was derived from reduction of sulfate and the ultimate alternative redox sink appeared to be down-stream of cysteine metabolism.
Fred R. Tabita, Dr (Advisor)
Birgit Alber, Dr (Committee Member)
Daniels Charles, Dr (Committee Member)
Joseph Krzycki, Dr (Committee Member)
93 p.
Microbiology
carbon assimilation: redox balance; CBB expression; nitrogenase complex; hydrogen production; sulfur metabolism, RubisCO; nonsulfur purple bacteria

Recommended Citations

Citations

  • Laguna, R. (2010). Interactive Control of Carbon Assimilation, Redox Balance, CBB Expression, Nitrogenase Complex Biosynthesis, Hydrogen Production, and Sulfur Metabolism in RubisCO Compromised Mutant Strains of Nonsulfur Purple Bacteria [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1285013415

    APA Style (7th edition)

  • Laguna, Rick. Interactive Control of Carbon Assimilation, Redox Balance, CBB Expression, Nitrogenase Complex Biosynthesis, Hydrogen Production, and Sulfur Metabolism in RubisCO Compromised Mutant Strains of Nonsulfur Purple Bacteria. 2010. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1285013415.

    MLA Style (8th edition)

  • Laguna, Rick. "Interactive Control of Carbon Assimilation, Redox Balance, CBB Expression, Nitrogenase Complex Biosynthesis, Hydrogen Production, and Sulfur Metabolism in RubisCO Compromised Mutant Strains of Nonsulfur Purple Bacteria." Doctoral dissertation, Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1285013415

    Chicago Manual of Style (17th edition)

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